Inkjet printing technology is used in many commercial products such as computer printers, graphics plotters, copiers, and facsimile machines. Herein, “inkjet printer” encompasses all of these devices. Some inkjet printers apply a backpressure to an ink reservoir to prevent ink from dripping from the printhead. In one approach, a vacuum source is used to apply the backpressure. This approach requires a permanently operating vacuum source. When the printer is not operative, e.g., shutdown over a weekend, the vacuum is not maintained. Failure to maintain backpressure causes ink to drip from the printhead and air to ingest into the printhead. In this case, the printhead may need to be re-primed, which is a costly and complicated procedure.
Prior-art backpressure systems based on the difference in the elevation of ink levels at which the interim and main ink supply tanks are placed suffer from ink leakage, since environmental conditions change and in particular temperature affect the ink volume and accordingly the ink level in a non-operating system. There is a need to improve the methods of backpressure generation and provide a method free of the above-mentioned drawbacks.
Herein, related art is described to facilitate understanding of the invention. Related art labeled “prior art” is admitted prior art; related art not labeled “prior art” is not admitted prior art.